Dendrites of the auditory brainstem nucleus, nucleus laminaris (NL), exhibit rapid and highly selective degeneration in response to lesioning of their afferent fibers in vivo, suggesting that neuronal input is necessary for the maintenance of NL dendrite structure. The goal of the proposed research is to use electrophysiology and live, multi-photon imaging techniques to dynamically study the cellular mechanisms involved in this process, in the same cell over time. With this system, the time course and nature of the change in NL dendrite structure will first be characterized. Calcium imaging methods will then be used in combination with morphometric analysis of NL dendrites to begin assessing whether changes in calcium are spatially and/or temporally correlated with input-specific changes in dendrite structure. Pharmacological studies will also be conducted in order to determine which molecules are necessary for inducing localized changes in NL dendrites. The Rho GTPases, important regulators of cytoskeletal organization, will be of particular interest. Finally, the reversibility of the change in dendrite structure will be assessed by replacing input to degenerating NL dendrites and assessing whether they are able to re-grow.